12P Pons-Brooks

Closest to Sun on 2024 April 21 at 0.78AU.
Closest to Earth on 2024 June 2 at 1.54AU.
Maximum magnitude 4.5 in April 2024
Orbital period 71 years (Halley type)


12P Pons Brooks at outburst on 2023 November 19.
Visual estimates at the time indicated comet was at 8th magnitude.

After the appearance of comet 1P Halley in 1986, I asked the question,
what is the next best "once in a lifetime" periodic comet?
The answer was 12P Pons-Brooks, but I had to wait another 37 years for it. The time has finally arrived.
The comet was initially discovered in 1812 by Jean-Louis Pons, a French astronomer,
and greatest visual comet discoverer of all time - 37 comets in total.
Then in 1883, the comet was recovered by William R Brooks,
a British born American astronomer and 2nd most prolific comet discoverer with 27 comets in total.
A recent paper in 2023 by Maik Meyer identified 12P at previous historical apparitions in 1457 and 1385CE.
It has an orbital period of 71 years and next arrives at perihelion on 2024 April 21 at 0.78AU.
There are several reasons why the comet is not as famous as Halley.
It has a larger perihelion distance (0.78AU) when compared to Halley (0.58AU).
It has a steep orbital inclination of 74 degrees (prograde) which means it doesn't spend a lot of time near the ecliptic.
It needs to arrive at perihelion during the month of December (+/- 3 months) for the appearance to be favourable one, closer to Earth.
An April arrival is less favourable, with the comet reaching closest proximity to Earth on 2024 June 2 at a rather large distance of 1.54AU.
Despite this, the comet is expected to still peak at magnitude 4 during the perihelion passage in April 2024.
Prior to perihelion in April 2024, the comet remains restricted to northern hemisphere observers.
Southern hemisphere observers will need to wait until late April 2024,
when the comet reappears low in the evening sky after dusk, on April 27.
Post perihelion, the comet will remain restricted to southern hemisphere observers
as the comet continues its southerly journey.
My observations will appear in chronological order, below the observing guide.

Comet 12P Pons-Brooks observing guide

This comet is notable for its regular outbursts. Magnitudes quoted below are a baseline value.
The comet could appear significantly brighter at any time. Outburst typically last several days,
followed by a return to baseline brightness.
Outbursts offer a tremendous level of detail in the nucleus, with spiral jets and horns potentially visible at any time.

January 2024
the comet remains restricted to northern hemisphere observers.
It is best observed in the evening sky after dusk, trekking eastwards through the constellation of Cygnus,
brightening from magnitude 8 to 7.
The best period of visibility is between January 1 to 15, then from January 29.
On January 10, it will be adjacent to dark nebula Barnard 145.
On January 13, it will be 30 south of the Crescent nebula NGC 6888.
On January 14, it will be 18 north of the open star cluster IC 4996.
On January 16, it will be 30 south of the open cluster Messier 29.

February 2024
the comet remains restricted to northern hemisphere observers.
It is best observed in the evening sky after dusk, trekking eastwards through the constellations of Cygnus,
Lacerta and Andromeda, brightening from magnitude 7 to 6.
The best period of visibility is between February 1 to 12, then from February 27.
No interesting rendezvous events occur this month.
 
March 2024
the comet remains restricted to northern hemisphere observers.
It is best observed in the evening sky after dusk, trekking eastwards through the constellations of Andromeda,
Pisces and Aries, brightening from magnitude 6 to 5.
The best period of visibility is between March 1 to 13, then from March 28.
On March 11, it will be 8 degrees south of the great Andromeda spiral galaxy M31.
On March 23, it will be 3 degrees south of the superb Triangulum spiral galaxy M33.
By March 31, the comet will be situated adjacent to Hamal (Alpha Arietis)

April 2024
the comet is initially observable from northern hemisphere skies but starts its journey southwards,
finally becoming visible to southern hemisphere observers by the end of the month.
It is best observed in the evening sky after dusk, trekking south-eastwards through the constellations of Aries
and Taurus, brightening from magnitude 5 to 4.5.
The best period of visibility is between April 1 to 10, and then from April 27.
On April 12, it will be 3 degrees west of Jupiter.
The comet reaches minimum solar elongation of 22 degrees on April 22 and will be a difficult object low in twilight.
Northerners lose sight of the comet.
Southerners get their first views around April 27, about an hour after sunset.
You will need a clear western horizon, preferably situated at a rural location.
The following 2 weeks offer the best period of visibility,
with the comet at its brightest and moonlight does not interfere with the view, offering naked eye views from a dark site.

May 2024
the comet remains restricted to southern hemisphere observers.
It is best observed in the evening sky after dusk, trekking south-eastwards through the constellations of
Taurus, Eridanus and Lepus, fading from magnitude 5 to 6.
The best period of visibility is between May 1 to 12, and then from May 26.
On May 10, it will be 1 degree west of Nu Eridanii.
On May 24, it will be adjacent to Lambda Lepii.
On May 29, it will be 1.3 degrees east of Arneb (Alpha Lepii)

June 2024
the comet remains restricted to southern hemisphere observers.
It is best observed in the evening sky after dusk, trekking south-eastwards through the constellations of
Lepus, Canis Major and Puppis, fading from magnitude 6.0 to 7.5.
The best period of visibility is between June 1 to 10, and then from June 24.
On June 3, it will be 1.3 degrees east of Delta Lepii.
On June 15, it will be adjacent to magnitude 11 spiral galaxy NGC 2280 in Canis Major.
On June 18, it will be 30 southwest of Epsilon Canis Majoris (Adhara)

July 2024
the comet remains restricted to southern hemisphere observers.
It is best observed in the evening sky after dusk, trekking eastwards through the constellations of
Puppis and Vela, fading from magnitude 7.5 to 9.0.
The best period of visibility is between July 1 to 9, and then from July 23.
On July 9-10, it will be a degree north of diffuse nebula NGC 2626 in Vela.
On July 31, it will be 1.3 degrees north of magnitude 6 globular cluster NGC 3201.

August 2024
the comet remains restricted to southern hemisphere observers.
It is best observed in the evening sky after dusk, trekking eastwards through the constellations of
Vela and Centaurus, fading from magnitude 9.0 to 10.5.
The best period of visibility is between August 1 to 8, and then from August 21.
On August 2, it will be 1.5 degrees south of the galaxy group NGC 3256_61_63.

September 2024
the comet remains restricted to southern hemisphere observers.
It is best observed in the evening sky after dusk, trekking eastwards through the constellation of
Centaurus, fading from magnitude 10.5 to 12.
The best period of visibility is between September 1 to 6, and then from September 19.
On September 12, it will be 1.3 degrees south of galaxy pair NGC 4835_4835A.
On September 15-16, it will be 2 degrees north of magnitude 9 spiral NGC 4945.
On September 23, it will transit the great globular cluster Omega Centauri (NGC5139)
but will likely be drowned out by the bright core. Either side of this date will be more preferable.

This may well be the last time 12P is visually observable.
It will next return to perihelion on August 11, 2095.
Unfortunately this will be another unfavourable appearance for the next generation of observers.
 

Comet 12P Pons-Brooks Observations

At its last return in 1954, it was notable for several, large pre-perihelion outbursts.
Sticking to form, the first reported outburst at the 2024 return was detected on 2023 July 20.82UT
My follow up observation a few hours later, on 2023 July 21 at 02:00UT indicated a +5 magnitude increase in brightness.
Initially stellar in appearance and magnitude 11.6, the outburst expanded and diffused out over the weeks following,
as it returned to pre-outburst levels (magnitude 16).
The comets heliocentric distance was 3.87AU, well beyond water ice sublimation.
This behaviour is very similar to the annual comet 29P Schwassmann-Wachmann and is likely due to
cryovolcanic activity on a large, slowly rotating nucleus involving highly volatile ices CO, CO2 and methane.
Another major eruption of +5 mag amplitude occurred on 2023 October 5 and on 2023 November 14.


12P on 2023 September 05
 


12P Pons-Brooks on 2023 July 24 at 21:55UT.
Taken remotely using ITEL T18 Nerpio Spain 0.32-m f/5.3 CDK + QHY600. 10 mins. FOV 10'. UCAC4 V=12.0. North up.
+96hrs post outburst. The horns, 35" long in PA010.
Coma diameter = 60"


Animation of 12P over 4 days , 2023 July 21-24

12P Pons-Brooks on 2023 July 23 at 21:30UT.
Taken remotely using ITEL T18 Nerpio Spain 0.32-m f/5.3 CDK + QHY600. 10 mins. FOV 10'. UCAC4 V=12.0. North up.
+72hrs post outburst. The horns, 30" long in PA008.
Coma diameter = 50"

12P Pons-Brooks on 2023 July 22 at 21:30UT.
Taken remotely using ITEL T18 Nerpio Spain 0.32-m f/5.3 CDK + QHY600. 10 mins. FOV 10'. UCAC4 V=11.9. North up.
+48hrs post outburst. The horns, 20" long in PA008, are starting to become more pronounced as the coma expands.
coma diameter = 35"

12P Pons-Brooks on 2023 July 21 at 21:30UT. Taken remotely using ITEL T18 Nerpio Spain 0.32-m f/5.3 CDK + QHY600. 10 mins. FOV 5'. UCAC4 V mag =11.9. North up.
24hrs post outburst. Note the development of a horseshoe shape, with horns directed northwards.
Coma diameter = 25"

12P Pons-Brooks in outburst on 2023 July 21 at 02:00UT.
Taken remotely using I-TEL Nerpio Spain T18 0.32-m f/5.3 astrograph + CCD. 10 min stack on comet. FOV 20'. North up.
V mag =11.8 using UCAC4 reference stars
G mag = 11.6 using GAIA DR2 reference stars
Coma diameter = 17"

 

5 day ephemeris

P/Pons-Brooks (12P)
          Date RA            declination   r     delta  mag Elong Phase Con
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 4 Dec 2023 12 18h32m38.64s +38 26' 28.3" 2.3468 2.5670 12.6 66.1 22.6 Lyr
 9 Dec 2023 12 18h42m37.18s +38 10' 28.8" 2.2847 2.5135 12.4 65.3 23.1 Lyr
14 Dec 2023 12 18h53m17.73s +37 58' 23.2" 2.2221 2.4587 12.2 64.6 23.6 Lyr
19 Dec 2023 12 19h04m42.25s +37 50' 08.6" 2.1591 2.4027 11.9 63.9 24.2 Lyr
24 Dec 2023 12 19h16m53.03s +37 45' 33.8" 2.0956 2.3459 11.7 63.2 24.8 Lyr
29 Dec 2023 12 19h29m53.02s +37 44' 20.3" 2.0317 2.2886 11.4 62.5 25.4 Cyg
 3 Jan 2024 12 19h43m45.69s +37 46' 05.1" 1.9673 2.2311 11.2 61.8 26.1 Cyg
 8 Jan 2024 12 19h58m34.70s +37 50' 18.0" 1.9025 2.1737 10.9 61.0 26.9 Cyg
13 Jan 2024 12 20h14m23.62s +37 56' 19.6" 1.8373 2.1168 10.6 60.1 27.7 Cyg
18 Jan 2024 12 20h31m15.73s +38 03' 15.3" 1.7717 2.0609 10.3 59.2 28.5 Cyg
23 Jan 2024 12 20h49m14.05s +38 09' 52.1" 1.7058 2.0063 10.0 58.1 29.3 Cyg
28 Jan 2024 12 21h08m21.22s +38 14' 41.1" 1.6396 1.9536 9.7 57.0 30.2 Cyg
 2 Feb 2024 12 21h28m38.75s +38 15' 59.4" 1.5733 1.9033 9.3 55.6 31.1 Cyg
 7 Feb 2024 12 21h50m06.23s +38 11' 49.8" 1.5068 1.8560 9.0 54.1 32.0 Cyg
12 Feb 2024 12 22h12m40.54s +38 00' 01.6" 1.4404 1.8119 8.7 52.4 32.9 Lac
17 Feb 2024 12 22h36m15.20s +37 38' 11.6" 1.3742 1.7717 8.3 50.5 33.7 Lac
22 Feb 2024 12 23h00m40.52s +37 03' 52.3" 1.3085 1.7357 7.9 48.4 34.4 And
27 Feb 2024 12 23h25m43.63s +36 14' 47.0" 1.2435 1.7043 7.6 46.1 35.0 And
 3 Mar 2024 12 23h51m08.85s +35 09' 01.3" 1.1796 1.6778 7.2 43.7 35.5 And
 8 Mar 2024 12 00h16m38.61s +33 45' 13.1" 1.1172 1.6561 6.8 41.0 35.7 And
13 Mar 2024 12 00h41m54.66s +32 02' 37.0" 1.0571 1.6393 6.4 38.3 35.6 And
18 Mar 2024 12 01h06m39.65s +30 01' 04.9" 0.9999 1.6270 6.1 35.5 35.3 Psc
23 Mar 2024 12 01h30m38.89s +27 41' 08.5" 0.9466 1.6187 5.7 32.6 34.6 Psc
28 Mar 2024 12 01h53m41.34s +25 03' 59.3" 0.8983 1.6137 5.3 29.9 33.6 Ari
 2 Apr 2024 12 02h15m40.02s +22 11' 22.2" 0.8565 1.6113 5.0 27.3 32.4 Ari
 7 Apr 2024 12 02h36m32.02s +19 05' 28.1" 0.8226 1.6102 4.8 25.2 31.2 Ari
12 Apr 2024 12 02h56m18.18s +15 48' 44.8" 0.7981 1.6094 4.6 23.5 30.1 Ari
17 Apr 2024 12 03h15m02.93s +12 23' 51.1" 0.7840 1.6077 4.4 22.7 29.6 Ari
22 Apr 2024 12 03h32m54.34s +08 53' 29.7" 0.7814 1.6046 4.4 22.8 29.9 Tau
27 Apr 2024 12 03h50m03.62s +05 20' 14.0" 0.7902 1.5994 4.5 23.8 30.9 Tau
 2 May 2024 12 04h06m44.18s +01 46' 11.9" 0.8100 1.5922 4.6 25.6 32.5 Tau
 7 May 2024 12 04h23m10.33s -01 47' 05.2" 0.8398 1.5834 4.9 28.1 34.4 Eri
12 May 2024 12 04h39m36.00s -05 18' 42.4" 0.8781 1.5737 5.1 31.0 36.3 Eri
17 May 2024 12 04h56m14.05s -08 48' 07.1" 0.9235 1.5641 5.5 34.2 38.0 Eri
22 May 2024 12 05h13m16.16s -12 14' 53.8" 0.9746 1.5555 5.8 37.6 39.4 Lep
27 May 2024 12 05h30m52.60s -15 38' 32.0" 1.0301 1.5493 6.1 41.1 40.3 Lep
 1 Jun 2024 12 05h49m11.96s -18 58' 18.0" 1.0890 1.5464 6.5 44.6 40.8 Lep
 6 Jun 2024 12 06h08m20.66s -22 13' 09.6" 1.1504 1.5481 6.9 48.0 41.0 Lep
11 Jun 2024 12 06h28m22.40s -25 21' 40.5" 1.2137 1.5552 7.2 51.3 40.7 CMa
16 Jun 2024 12 06h49m18.18s -28 21' 59.6" 1.2783 1.5685 7.6 54.3 40.2 CMa
21 Jun 2024 12 07h11m06.27s -31 12' 01.5" 1.3437 1.5889 7.9 57.1 39.4 CMa
26 Jun 2024 12 07h33m41.99s -33 49' 41.8" 1.4097 1.6168 8.3 59.7 38.5 Pup
 1 Jul 2024 12 07h56m57.60s -36 13' 14.5" 1.4760 1.6525 8.6 61.8 37.4 Pup
 6 Jul 2024 12 08h20m42.13s -38 21' 23.9" 1.5425 1.6960 9.0 63.6 36.2 Pup
11 Jul 2024 12 08h44m41.98s -40 13' 28.3" 1.6089 1.7472 9.3 65.1 35.0 Vel
16 Jul 2024 12 09h08m42.25s -41 49' 22.1" 1.6751 1.8059 9.6 66.1 33.7 Vel
21 Jul 2024 12 09h32m28.20s -43 09' 36.7" 1.7412 1.8715 10.0 66.7 32.4 Vel
26 Jul 2024 12 09h55m46.50s -44 15' 15.8" 1.8069 1.9436 10.3 67.0 31.2 Vel
31 Jul 2024 12 10h18m26.00s -45 07' 49.6" 1.8723 2.0216 10.6 66.9 29.9 Vel
 5 Aug 2024 12 10h40m17.94s -45 49' 02.3" 1.9373 2.1049 10.9 66.4 28.7 Vel
10 Aug 2024 12 11h01m16.16s -46 20' 39.0" 2.0018 2.1927 11.2 65.7 27.5 Vel
15 Aug 2024 12 11h21m17.18s -46 44' 18.8" 2.0660 2.2844 11.5 64.7 26.3 Cen
20 Aug 2024 12 11h40m19.92s -47 01' 31.8" 2.1296 2.3793 11.8 63.5 25.2 Cen
25 Aug 2024 12 11h58m25.38s -47 13' 38.5" 2.1929 2.4768 12.1 62.0 24.0 Cen